Remove early NaN/Infinity check in MathPowStub.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 3550d3bb0d72c3fe05f2c3c9504dc0da4174d885..3b9d14831ad564f3dd665f1f369c85efb7e5472c 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -7414,6 +7414,9 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_Math_pow) {
   }
 
   CONVERT_DOUBLE_ARG_CHECKED(y, 1);
+  // Returning a smi would not confuse crankshaft as this part of code is only
+  // run if SSE2 was not available, in which case crankshaft is disabled.
+  if (y == 0) return Smi::FromInt(1);  // Returns 1 if exponent is 0.
   return isolate->heap()->AllocateHeapNumber(power_double_double(x, y));
 }